Oriane Jouno runs her finger over the palm-sized pseudo blossom of the Hong Kong dogwood. As if painted, the colour turns from cream to a pale pink. “It is one of our rare woody plants in the park,” says the 35-year-old Frenchwoman, who manages the huge Parc Botanique de Haute Bretagne near Fougères with her family. It was her plant-crazy father Alain Jouno who set up the park in the eastern part of Brittany, on France’s northwest Atlantic coast in 1994. Where earlier only scrub grew, today 24 theme gardens celebrate the art of landscaping. The Japanese garden near the manor house with its met…